Polling vs Push vs Persistent Connections for Mobile

Side by side

Criterion	Periodic polling / sync on foreground	Push notifications (APNs/FCM)	Persistent connection (WebSocket/SSE)
Latency	Interval / on open	Seconds (best effort)	Sub-second
Works in background	Only via OS-scheduled tasks	Yes (visible) / throttled (silent)	No (except special cases like VoIP)
Battery & data cost	Depends on interval	Low	Medium–high while connected
Delivery guarantee	Yes when it runs	No	While connected; resync after reconnect
Server cost	Request volume	Push provider calls, token hygiene	Connection fan-out infrastructure
User permission	None	Required for visible notifications	None

When to choose each

Periodic polling / sync on foreground

App fetches changes on launch, on foreground and occasionally while open.

Choose when

Data that changes rarely
Guaranteed freshness when the user opens the app

Avoid when

Time-sensitive updates while the app is backgrounded

Push notifications (APNs/FCM)

Platform push wakes the user or app; payload is a hint or a short message.

Choose when

Messages and alerts users must see
Background 'sync now' hints

Avoid when

Delivery guarantees or large payloads
High-frequency updates (throttled)

Persistent connection (WebSocket/SSE)

Open socket while the app is in the foreground.

Choose when

Chat, live tracking, collaboration on screen
Sub-second updates

Avoid when

Background updates (OS suspends sockets)
Battery-sensitive idle screens

Combine them: sync on foreground for correctness, push for timely background awareness (as hints, never as the source of truth), and persistent connections only for screens that need live updates while open. Always design a resync path because push and sockets both drop messages.

Polling vs Push vs Persistent Connections for Mobile

Side by side

When to choose each

Periodic polling / sync on foreground

Push notifications (APNs/FCM)

Persistent connection (WebSocket/SSE)

Verdict

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Sources